Process for the manufacture of polycarbonate-oligomers without solvent

ABSTRACT

Polycarbonate oligomers having hydroxy end groups are produced by a melt reaction with bisphenol-A and a basic catalyst. The oligomers may then be reacted with chloro end-group siloxanes in the presence of a solvent and an acid acceptor to yield polycarbonate-polysiloxane block co-polymers. The melt reaction occurs at elevated temperature without the direct use of phosgene gas.

BACKGROUND OF THE INVENTION

The present invention relates to a method for makingsilicone-polycarbonate block co-polymers. In particular, the inventionrelates to a method whereby polycarbonate oligomers having terminalhydroxy groups are produced by a melt reaction of polycarbonate resinwith a dihydric phenol in the presence of a catalyst and in the absenceof an organic solvent. The oligomers are thereafter combined withpolyorganosiloxanes having terminal chloro-organo siloxy groups toproduce the block co-polymers. The method employed is effective toproduce the block co-polymers without directly using phosgene gas in thefinal synthesis.

A siloxane polycarbonate resin can be made in a two-step processinvolving first reacting chloro end group siloxane oligomers with anexcess of bisphenol-A (BPA), then reacting the resulting phenolichydroxy end group siloxane with additional BPA and phosgene in aconventional interfacial phosgenation reaction to yield the desiredblock co-polymer. One such useful polycarbonate-polydimethylsiloxaneblock co-polymer contains 43 weight percent siloxane units with anaverage block length of about 10. The material has utility as an impactmodifier in blends with polycarbonate resin and as a film used as aninterlayer in multilayer laminates of polycarbonate resin sheets andacrylic resin sheets. Typically, these laminates consist of two or morelayers of polycarbonate sheet, optionally with an internal layer ofacrylic sheet, with the resin interlayers serving as an adhesive and asa spacer to separate the sheets.

In a particular process set forth in Vaughn, U.S. Pat. No. 3,189,662,assigned to the Assignee herein and incorporated herein by reference,silicone-polycarbonate block co-polymers are made by phosgenating amixture of dihydric phenol terminated polydiorganosiloxane and dihydricphenol in the presence of an organic solvent and an acid acceptor.Although the method results in the production of silicone-polycarbonateblock copolymers useful in a variety of applications, such as injectionmoldable thermoplastics and elastomers having improved tensileproperties, the method requires the direct use of phosgene gas in thefinal synthesis.

Silicone-poly(arylcarbonate) block co-polymers can be made withoutdirectly using phosgene gas in the final synthesis of the blockco-polymer as set forth in Evans, U.S. Pat. No. 4,920,183, assigned tothe Assignee herein. A hydroxyaryl terminated poly(arylcarbonate)oligomer having an average of about 2 to about 1,000 chemically combinedarylcarbonate units is interconnected with a chlorine terminatedpolydiorganosiloxane having an average of about 2 to about 1,000chemically combined diorganosiloxy units, in the presence of an organicsolvent and an acid acceptor. The silicone-poly(arylcarbonate) blockco-polymer is recovered from the mixture for example by addition of thereaction mixture to a precipitating solvent such as methanol.

Evans et al. '183, also discusses the manufacture of hydroxyaryloligomers. According to Evans et al., these oligomers can be made byeffecting the polymerization of cyclic arylcarbonates in the presence ofphenol or bisphenol-A (BPA) as shown in U.S. Pat. No. 4,849,502,assigned to the Assignee herein and incorporated by reference.

Evans et al. discusses another procedure which can be used to makehydroxyaryl oligomers by the controlled reaction in a suitable solventof high molecular weight polycarbonate resin with a phenol or polyhydricphenol and a polymerization initiator, such as alkaline metal phenoxideor polycarbonate formation catalysts as set forth in Brunelle et al.,U.S. Pat. No. 4,644,053, assigned to the Assignee herein andincorporated by reference.

Chlorine terminated polydiorganosiloxane can be made by known proceduressuch as by the controlled hydrolysis of diorganodihalosilane, forexample, dimethyldichlorosilane set forth in U.S. Pat. Nos. 2,381,366and 2,629,726. Another procedure which can be employed to make chlorineterminated polydiorganosiloxane is the equilibration of a mixture ofdiorganochlorosilane and a cyclic polydiorganosiloxane, for example,octamethylcyclo-tetrasiloxane, in the presence of a metal catalyst suchas ferric chloride as set forth in U.S. Pat. No. 2,421,653.

Japanese patent application no. 60-114576 discloses a process to producelow molecular weight polycarbonates having terminal hydroxy groupsproduced by the reaction of high molecular weight polycarbonates withhydroxy compounds, e.g. 1,6-hexane diol and diethylene glycol. Although2,2-bis(4-hydroxyphenyl)propane is disclosed within a long list ofpossibly useful candidate hydroxy compounds, it is not mentioned as apreferred compound. No disclosure is made in the reference as to theratio of bisphenol-A to polycarbonate. The reference also fails todisclose reacting a hydroxyaryl terminated polycarbonate oligomer with apolydiorganosiloxane to form a polycarbonate-polysiloxane blockco-polymers. Industry is currently seeking simplified processes forproducing silicone-polyarylcarbonate block co-polymers with reducedsolvents and without the direct use of phosgene gas.

SUMMARY OF THE INVENTION

The present invention is based upon the discovery that a hydroxyterminated polycarbonate oligomer can be produced by a melt reaction ofa polycarbonate resin with a bisphenol-A in the presence of a basiccatalyst and in the absence of a solvent. The mole ratio of BPA topolycarbonate is in the preferred range of about 1:50 to about 5:10 andpreferably about 2:10 to about 4:10. The hydroxy terminatedpolycarbonate oligomer may thereafter be reacted with a chlorineterminated polyorganosiloxane in the presence of an organic solvent andan acid acceptor to yield a silicon polycarbonate copolymer without thedirect use of phosgene. In a particular embodiment, the polycarbonateoligomers are combined with silicone compositions to producesilicone-polycarbonate block co-polymers.

DESCRIPTION OF THE INVENTION

The invention relates to the solventless manufacture of usefulpolycarbonate oligomers without directly using phosgene. The oligomersmay be relatively short hydroxyaryl terminated polycarbonate oligomershaving an average of about 2 to about 50, preferably 2 to about 15, morepreferably about 3 to about 6, chemically combined carbonate units. Thepolycarbonate oligomers are produced by a melt reaction of apolycarbonate resin with a dihydric phenol such as bisphenol-A (BPA),i.e., 2,2-bis(4-hydroxy-phenyl propane) in the absence of a solvent andwithout directly using phosgene gas. The mole ratio of BPA topolycarbonate is preferably in the range of about 1:50 to about 5:10 andmore preferably about 2:10 to about 4:10. As used herein throughout theterm polycarbonate, in the expression mole ratio of BPA topolycarbonate, should be understood to mean polycarbonate repeat unitsin the polymer chain. The polycarbonate oligomers are reacted with achlorine terminated polyorganosiloxane having an average of about 2 toabout 100, preferably about 5 to about 60 and more preferably about 7 toabout 12, chemically combined organosiloxy units in an organic solventto form the silicone polycarbonate block co-polymer.

In the invention, a high molecular weight polycarbonate resin is used asa starting material and is melt reacted with BPA to producepolycarbonate oligomers with hydroxy end groups. The polycarbonateoligomers thus produced may be used without directly using phosgene gasin the final synthesis of the block co-polymers. The terms"polycarbonate resins" and "dihydric phenol" are well known and havebeen defined in detail in U.S. Pat. Nos. 4,960,863; 4,973,665 and4,999,408, all of which are incorporated herein by reference.

The polycarbonate (PC) resin may be one of many available materialshaving an intrinsic viscosity ranging from about 0.4 to about 1.6 dl/gin methylene chloride at 25° C. and a molecular weight ranging fromabout 20,000 to about 100,000. In the examples below, a blend of PCresins having intrinsic viscosities of 0.6 and 1.5 dl/g are used, andthe PC oligomers have an average chain length of about 4 carbonateunits.

The formation of silicone-polycarbonate co-polymers occurs by reactionof the hydroxyaryl oligomers and the chlorine terminatedpolydiorganosiloxanes at elevated temperatures in the presence of anorganic solvent (e.g., methylene chloride) and an acid acceptor (e.g.,triethylamine). The order of addition of the reaction is not critical.Reaction temperatures which can be used range from about 15° C. to about40° C. Recovery of the silicone polycarbonate block co-polymer can beeffected by the addition of the reaction mixture to a precipitatingsolvent such as methanol, or by steam precipitation.

The silicone polycarbonate block co-polymer made by the method of theinvention can be used as a laminating agent for polycarbonates, and asan impact modifier in blends with polycarbonate and other resins.

The polyorganosiloxane material may have a chain length ranging fromabout 2 to about 100, preferably about 5 to about 60 and more preferablyabout 7 to about 12. In the examples below, the polyorganosiloxane is apolydimethylsiloxane (PDMS) having an average chain length of about 8 toabout 10 dimethylsiloxane units, also known as D units.

In order that those skilled in the art would be better able to practicethe invention, the following examples are given by way of illustrationand not by way of limitation.

Method 1 PC oligomer preparation (small scale)

A blend of 300 g of polycarbonate resin (intrinsic viscosity of 0.57dl/g at 25° C. in methylene chloride) and 0.7 g (0.00125 mole) oftetrabutylammonium tetraphenylborate was intensively mixed for 30seconds in a type FM 10L mixer manufactured by Rheinstahl Henschel AG.To that blend was then added 970 g additional polycarbonate resin of thesame grade (total of 1270 g, 5 moles) and 342 g (1.5 moles) bisphenol-A.After thorough blending, that mixture was introduced into a model ZSK-30 twin screw extruder manufactured by Werner Pfleiderer Co. operatedat 260° C. The oligomer product exited the extruder as a liquid streamand was collected by quenching in water. The oligomers werecharacterized by gel permeation chromatography (GPC) (see table).

Method 2 PC oligomer preparation (large scale)

A blend of 1.36 kg of polycarbonate resin (intrinsic viscosity of 0.57dl/g) and 6.45 g of tetramethylammonium hydroxide pentahydrate wasintensively mixed for 30 seconds as in Method 1. This was repeated, andthe 2.73 kg of catalyst-containing blend was then mixed in a ribbonblender with 8 kg of the same grade of polycarbonate resin, 60.9 kg ofhigh molecular weight polycarbonate resin (intrinsic viscosity of 1.5dl/g) and 19.2 kg of bisphenol-A. The mixture was then melt processed inan extruder as described in Method 1 at a temperature of 277° C. Theoligomer product exited the extruder as a liquid stream which wascollected by contacting with the chilled stainless steel rolls (two 6inch diameter counter-rotating rolls) of a standard dual roll flakerdevice. The oligomers were characterized by GPC.

    __________________________________________________________________________               RESIN                                                                 BPA/PC Unit   End Capping                                                                          Catalyst                                                                            GPC.sup.(3)                                                                           Corrected.sup.(4)                       Ex..sup.(5)                                                                      Mole Ratio                                                                            Grade.sup.(1)                                                                       (Mole %)                                                                             (Mole %)                                                                            MW  MN  MN                                      __________________________________________________________________________    1  1/10    100% PC1                                                                            2.3%   0.025%.sup.(6)                                                                      6300                                                                              1400                                                                              1620                                    2  2/10    100% PC1                                                                            2.3%   0.025%.sup.(6)                                                                      3800                                                                              700 870                                     3  3/10    100% PC1                                                                            2.3%   0.025%.sup.(6)                                                                      2400                                                                              500 660                                     4  3/10    25% PC1                                                                             0.7%.sup.(2)                                                                         0.025%.sup.(6)                                                                      28400                                                                             4500                                                                              4960                                               75% PC2                                                            5  3/10    25% PC1                                                                             0.7%   0.025%.sup.(7)                                                                      2500                                                                              500 660                                                75% PC2                                                            6  3/10    25% PC1                                                                             0.7%   0.1%.sup.(7)(8)                                                                     1500                                                                              500 660                                                75% PC2                                                            7  3/10    25% PC1                                                                             0.7%   0.005%.sup.(7)                                                                      7700                                                                              640 810                                                75% PC2                                                            8  3/10    25% PC1                                                                             0.7%   0.01%.sup.(7)                                                                       6700                                                                              900 1090                                               75% PC2                                                            9  3/10    25% PC1                                                                             0.7%   0.025%.sup.(7)                                                                      1800                                                                              500 660                                                75% PC2                                                            10 3/10    25% PC1                                                                             0.7%   0.025%.sup.(7)(9)                                                                   2600                                                                              550 710                                                75% PC2                                                            11 3/10    25% PC1                                                                             0.7%   0.025%.sup.(7)(9)                                                                   2600                                                                              550 710                                                75% PC2                                                            12 4.8/10  25% PC1                                                                             0.7%   0.025%.sup.(7)                                                                      2300                                                                              500 740                                                75% PC2                                                            13 3/10    25% PC1                                                                             0.7%   0.025%.sup.(7)                                                                      2700                                                                              500 770                                                75% PC2                                                            14 1.3/10  25% PC1                                                                             0.7%   0.025%.sup.(7)                                                                      8000                                                                              700 1340                                               75% PC2                                                            __________________________________________________________________________     .sup.(1) PC1 resin and PC2 resin had IV's respectively of 0.57 and 1.5        dl/g.                                                                         .sup.(2) Calculated mole %, based on 2.3 mole % end capping in PC1 and        0.17 mole % end capping in PC2.                                               .sup.(3) MW = Weight Average Molecular Weight                                 MN = Number Average Molecular Weight                                          Data as generated by Gel Permeation Chromatograph (GPC). Gel Permeation       chromatography analysis was carried out on a Watters Associates Model 150     instrument fitted with two ultrastyragel linear columns and one 500           angstrom ultrastyragel column using chloroform as solvent. The instrument     was calibrated using bisphenolA polycarbonate resin standards. The            molecular weight data is reported under "GPC" in the table is the data        generated directly by the GPC analysis. Since, however,  the calibration      of the system was not specifically for the very low molecular weight          materials being analyzed for here, a second number average molecular          weight value, indicated as the "corrected MN" in the table, is also           reported. This was done by reassigning MN of 228, 482, 736 and 990 which      are, respectively, the molecular weights of bisphenolA and the three          lowest hydroxy end group polycarbonate oligomers, to the four lowest MN       peaks generated in the GPC analysis.                                          .sup.(4) MW data after reassignment of MW 228, 482, 736 and 990 (i.e. BPA     "dimer", "trimer", "tetrimer") to the four low MW peaks in the GPC.           .sup.(5) Ex. 1-14 Method 1. Ex. 16 Method 2.                                  .sup.(6) Tetrabutylammonium tetraphenylborate used as catalyst.               .sup.(7) Tetramethylammonium hydroxide pentahydrate used as catalyst.         .sup.(8) Oligomers had a yellow color.                                        .sup.(9) Examples 10 and 11 differ in that for 10, the catalyst was           premixed with the PC1 and for 11, the catalyst was premixed with the blen     of PC1 and PC2.                                                          

Examples 1-3 vary the mole ratio of BPA/PC between 1:10 and 3:10.Examples 12-14 show a wider range of BPA/PC mole ratios between 1:10 and4.8:10, with the amount of catalyst and resin being held constant. AddedBPA lowers the molecular weight of the oligomers.

Examples 4-6 show that different catalysts cause different resultsgenerally. The borate catalyst performed well with the low molecularweight, low viscosity (high end capping) PC1 resin of Examples 1-3, butwas not as effective with the high molecular weight, high viscosity (lowendcapping) PC2 resin of Example 4. The tetramethylammoniumhydroxide(ammonium based catalyst) does not exhibit the same variation in resultsas the borate catalyst.

Examples 5-9 show an effective range of ammonium based catalyst, withExample 9 being about optimal for the conditions shown. Molecular weightgoes to a minimum at about 0.025 mole percent catalyst. Additionalcatalyst causes yellowing. Basic catalysts of various well known kindsmay be used in effective amounts, for example, about 0.005 to about 0.1mole percent to achieve the desired results. The basic catalysts used inthe preparation of polycarbonate oligomers are any of the well-known andconventional basic catalysts. These catalysts include the organic andinorganic bases. Some illustrative and non-limiting examples of organicand inorganic base catalysts include lithium hydroxide, sodiumcarbonate, sodium acetate, sodium methylate, sodium borohydride,isopropyl amine, sodium phenoxide, sodium aluminumhydride and alkylammonium hydroxides such as tetramethylammonium hydroxide andtetraethylammonium hydroxide. Also included are compounds such astetraalkylammonium tetraphenylborates that are known to convert to basiccatalysts at the elevated temperatures used in the preparation of thepolycarbonate oligomers.

The present invention employs polycarbonate as a raw material to producepolycarbonate oligomers in an extrusion reaction without solvent orphosgene. The oligomers are combined with siloxanes to produce desiredpolycarbonate-siloxane co-polymers.

While there has been described what at present are considered to be thepreferred embodiments of the present invention, it will be readilyapparent to those skilled in the art that various changes andmodifications may be made therein without departing from the inventionand it is intended in the appended claims to cover such changes andmodifications as fall within the true spirit and scope of the invention.

What is claimed:
 1. A method for making a polycarbonate polysiloxane block co-polymer comprising melt reacting a polycarbonate resin having an intrinsic viscosity ranging from about 0.4 to about 1.6 dl/g in methylene chloride at 25° C. and bisphenol-A in the presence of a basic catalyst and in the absence of both a solvent and phosgene to produce a hydroxyaryl terminated polycarbonate oligomer having an average of about 2 to about 50 chemically combined carbonate units, wherein the mole ratio of bisphenol-A to polycarbonate is in the range of about 1:50 to about 5:10 and reacting the hydroxyaryl terminated polycarbonate oligomer and a chlorine terminated polyorganosiloxane under substantially anhydrous conditions in an organic solvent and in the presence of an acid acceptor.
 2. The method according to claim 1, wherein the polyorganosiloxane has an average chain length of 2 to about 100 chemically combined organosiloxy units.
 3. The method according to claim 1, wherein the polyorganosiloxane has an average chain length of 5 to about 60 chemically combined organosiloxy units.
 4. The method according to claim 1, wherein the polyorganosiloxane has an average chain length of 7 to about 12 chemically combined organosiloxy units.
 5. The method according to claim 1, wherein the polyorganosiloxane is a chlorine terminated polydimethylsiloxane having about 8 to about 10 dimethylsiloxane units.
 6. The method according to claim 1, wherein the basic catalyst comprises at least one member selected from the group consisting of:tetrabutylammonium tetraphenylborate, tetraethylammonium hydroxide, and tetramethylammonium hydroxide.
 7. The method according to claim 1, wherein the catalyst is present in a range of from about 0.005 to about 0.1 mole percent.
 8. A polycarbonate-polysiloxane block co-polymer prepared by the method of claim 1 wherein the chlorine terminated polyorganosiloxane has an average of about 2 to about 100 chemically combined organosiloxy units wherein the co-polymer is free of phosgene.
 9. The polycarbonate-polysiloxane copolymer of claim 8, wherein the polyorganosiloxane has an average of about 2 to about 60 chemically combined organosiloxy units.
 10. The polycarbonate-polysiloxane copolymer of claim 8, wherein the polyorganosiloxane has an average of about 5 to about 60 chemically combined organosiloxy units.
 11. The polycarbonate-polysiloxane copolymer of claim 8, wherein the polyorganosiloxane has an average of about 7 to about 12 chemically combined organosiloxy units.
 12. The polycarbonate-polysiloxane copolymer of claim 8, wherein the polyorganosiloxane comprises a chlorine terminated polydimethylsiloxane having about 8 to about 10 dimethylsiloxane units.
 13. A method for making a polycarbonate polysiloxane copolymer comprising melt reacting a polycarbonate resin and a dihydric phenol in the presence of a basic catalyst and in the absence of a solvent and phosgene to produce a hydroxyaryl terminated polycarbonate oligomer having an average of about 2 to about 50 chemically combined carbonate units: andreacting the hydroxyaryl terminated polycarbonate oligomer and a chlorine terminated polydiorganosiloxane in an organic solvent and in the presence of an acid acceptor to form a polycarbonate-polysiloxane block co-polymer free of phosgene.
 14. The method according to claim 13, wherein the dihydric phenol is bisphenol-A (BPA).
 15. The method according to claim 13, wherein the polycarbonate oligomer has from about 2 to about 15 carbonate units.
 16. The method according to claim 13, wherein the polycarbonate oligomer has from about 3 to about 6 carbonate units.
 17. The method according to claim 13, wherein the mole ratio of BPA to polycarbonate is-about 2:10 to about 4:10.
 18. The method according to claim 13, wherein the catalyst comprises at least one member selected from the group consisting of:tetrabutylammonium tetraphenylborate, tetraethylammonium hydroxide, and tetramethylammonium hydroxide.
 19. The method according to claim 13, wherein the catalyst is present in a range from about 0,005 to about 0.1 mole percent.
 20. A polycarbonate-polysiloxane block copolymer prepared by reacting a hydroxy terminated polycarbonate oligomer made by the melt reaction of a polycarbonate resin and a dihydric phenol in the presence of a basic catalyst and in the absence of a solvent and a chlorine terminated polyorganosiloxane having an average of about 2 to about 100 chemically combined organosiloxy units in an organic solvent.
 21. The copolymer according to claim 20, wherein the dihydric phenol is bisphenol-A.
 22. The copolymer according to claim 20, wherein the polycarbonate oligomer has from about 2 to about 15 carbonate units.
 23. The copolymer according to claim 20, wherein the polycarbonate oligomer has from about 3 to about 6 carbonate units.
 24. The copolymer according to claim 21, wherein the mole ratio of bisphenol-A to polycarbonate is about 2: 10 to about 4:10. 